Improved alkalimetric monitoring for anaerobic digestion of high-strength wastes

Abstract

Alkalinity measurements to pH endpoints of 5.75 and 4.3 were used to evaluate process stability of anaerobic digesters that treat a high-strength waste of various HRTs and feed concentrations. Total volatile acids concentrations, which varied between 500 mg/l as HAc during steady-state periods and nearly 10,000 mg/l as HAc during stress periods, correlated strongly with intermediate alkalinity (from pH 5.75 to 4.3). Partial alkalinity (to pH 5.75) was used to approximate bicarbonate concentration. Combination of both alkalinites into an IA: PA ratio greatly increased the sensitivity of the alkalinity test, and provided a simple, inexpensive parameter to detect process upset and recovery.